Viability of Pseudocapillaria tomentosa Eggs Exposed to Heat, Ultraviolet Light, Chlorine, Iodine, and Desiccation

Pseudocapillaria tomentosa is an important pathogen in zebrafish facilities. We investigated heat, ultraviolet (UV) light, chlorine, iodine, and dessciation for killing the parasite's eggs. Eggs released with feces larvate in about 5-10 days, and treatments were evaluated by exposing fresh eggs and subsequently comparing larvation to untreated eggs as an indication of survival. Collectively, untreated eggs in all trials showed high levels of survival. Eggs were exposed to elevated temperatures (40°C, 45°C and 50°C) for 1, 8, or 24 h, which resulted in substantial reduction in viability of eggs. UV radiation was effective, with no larvation at 50-300 mWs/cm² and <2% at 20 mWs/cm². Three chlorine products (JT Baker, Clorox^®, and Bi-Mart) were tested at 25, 50, 100, 500, and 3,000 ppm (pH 7.0-7.3) with 10 min exposure. All were effective at 500 or 1,000 ppm. There was variability between three products and trials at lower concentrations, but overall chlorine was not very effective at 25-100 ppm except for Bi-Mart brand at 100 ppm. Povidone-iodine was not effective at 25 or 50 ppm for 10 min, but was effective at 200 ppm for 1 h. Desiccation was effective, and no eggs larvated after 2 h drying.